1. Field of the Invention
The present invention relates generally to a semiconductor device, and more particularly, to a semiconductor device implemented a charge share countermeasure without adding a PMOS transistor for precharge.
2. Description of Related Art
FIG. 9 is a circuit diagram illustrating a semiconductor device of a related art. This semiconductor device includes a PMOS transistor 103 coupled to a power source and an NMOS transistor 105 coupled to the ground voltage. Furthermore, the gates of these transistors ate connected to a clock generator not shown in the drawing. The clock generator generates a clock signal CLK and inputs it to the gates of these transistors. An NMOS transistor 107 and an NMOS transistor 108 are connected in series between the PMOS transistor 103 and NMOS transistor 105. The circuit including these transistors is referred to as a dynamic circuit. A wire 109 is connected between the PMOS transistor 103 and NMOS transistor 107 and inverter 110 are connected to the wire 109. Based on inputting to the gates of the NMOS transistor 107 and NMOS transistor 108, the PMOS transistor 103 precharges the wire 109 and the NMOS transistor 105 discharges it. In this way, the inverter 110 operates accordingly.
However, this dynamic circuit has the following problem. Depending on the combination of the signals input to the gates of the NMOS transistor 107 and NMOS transistor 108, the electric charge at the wire 109 may transfer to a node 303 between the NMOS transistor 107 and NMOS transistor 108. Accordingly, there is a possibility of the inverter 110 malfunctioning since the voltage of the wire 109 gets lowered. This phenomenon is called charge share.
Consequently, in a conventional technique, the voltage of the wire 109 is prevented from being lowered by providing at the node 303, and similarly to the wire 109, a PMOS transistor 301 for precharge to make the voltages of the node 303 and wire 109 approximately equal.
However, with a conventional semiconductor device, since the node 303 is precharged by connecting the PMOS transistor 301, the capacity of the entire dynamic node is increased by the additional PMOS transistor 301. This results in affecting the operational speed of the dynamic circuit.